The Snapshot Shuttle (for Snapshot //e card)A Multi-tasking System for Apple II+ and IIe by Bob Sather (1984 Dark Star Systems)
"The Snapshot Shuttle lets you use several programs at a time without the need to swap disks or reboot. It is the most effective and least expensive method of adding multi-tasking capabilities to your microcomputer."
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Video demonstration of Snapshot Shuttle in action is here:-https://youtu.be/U7hTfkaxYyw